Adaptation of redox metabolism in drug-tolerant persister cells is a vulnerability to prevent relapse in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) remains a major unresolved disease because of its remarkable therapeutic resistance. Even patients who respond to initial therapy experience relapse in most cases. The mechanisms underlying therapy-acquired resistance supporting relapse are poorly understood. In this study, we aimed to determine the metabolic features of PDAC during relapse, specifically adaptations of mitochondrial and redox metabolism. We used preclinical PDAC mouse models (patient-derived xenografts and murine syngeneic allografts) that present complete regression under initial chemotherapeutic treatment but relapse after a certain time. Relapsed tumors were analyzed ex vivo by flow cytometry to measure mitochondrial and redox characteristics. Molecular mechanisms were investigated by quantification of ATP and antioxidants levels, RT-qPCR and bulk RNA-sequencing. Our findings show that mitochondrial metabolism is reprogrammed during relapse, with increased mitochondrial mass, ATP levels, mitochondrial superoxide anions, and total ROS levels, in relapsed compared to control tumors in both models; mitochondrial membrane potential is increased in the xenografts model only. This mitochondrial metabolic reprogramming occurs during treatment-induced regression and at relapse onset. At the molecular level, antioxidant defenses are increased in relapsed tumors and during treatment. These data suggest that treatment-induced oxidative stress may cause the appearance of treatment-adapted cells, known as drug-tolerant persister (DTP) cells. Finally, the combined treatment of arsenic trioxide (ROS inducer) and buthionine sulfoximine (glutathione synthesis inhibitor) is able to completely prevent relapse in PDAC xenografts. In conclusion, targeting redox metabolism via ROS production and antioxidant inhibition is a very promising approach to prevent relapse in PDAC patients. Significance Mitochondrial and redox metabolisms are reprogrammed during treatment-acquired resistance in pancreatic cancer promoting the survival of drug-tolerant persister cancer cells, opening up new avenues for better therapeutic management of patients. ### Competing Interest Statement The authors have declared no competing interest.